Gas analyzer



Oct. 3, 1939.

D. LABINO 2,174,923

GA S ANALYZ ER Filed June 30, 195'? REC-0R DER 1a -i l l l l l Dominic/rL abz'no AT RNEYS INVENTOR Patented Oct. 3, 1939 UNITED STATES GASANALYZER Dominick Labino, Clarion, Pa., assignor to Owens- IllinoisGlass Company, a corporation of Ohio Application June 30, 1937, SerialNo. 151,146

7 Claims.

The present invention relates to a method and apparatus for detectingthe presence of and degree of combustion, and more particularly foranalyzing automatically and continuously the combustible gas content ofwaste gases emanating from a gas fired furnace.

One of the objects of the invention is to provide a method and apparatusfor indicating and recording the combustible gas contents such as 10carbon monoxide, hydrogen, hydrocarbons, or the like, that are found bytest in the canals of gas fired furnaces, such as a glass furnace, orthe like. These gases in percentage should be very low at all times,and, for highest efliciency, none of these gases should be present.However, the percentage of carbon monoxide alone shown by Orsat analysisranges generally from about zero to two or three per cent or sometimesmore. By

continuously indicating and recording the percentage of combustibles inthe waste gases, ad-

justments may be made to keep the combustlbles as low as possible, andat the same time avoid an excess of air over the optimum proportions.

Heretofore various means have been provided for electrically analyzingthe combustibles present in stack gases, as, for example, by registeringthe ohmic resistance of a platinum wire which is raised to ignitiontemperature, and is placed in a cell in which samples of the stack gasesare continuously passing. This method I have found to be inaccurate andunreliable after a short period of time owing apparently to the attackof the gases upon the platinum wire which seems to be changed in itscatalytic behavior. It is an object of the invention to overcome thesediiiiculties and to provide an instrument which will continuously andaccurately record the percentage of combustibles present, and to do thisfor a long period of time.

Another object of the invention is to provide an apparatus for thispurpose which is extremely simple and inexpensive, and may beconstructed and put into operation at a cost far below that whichhasheretofore been found possible for this type of apparatus. In thisconnection I aim to eliminate the use of chemicals or other expensivesubstances which have heretofore been used as, for example, those usedin an Orsat apparatus tc analyze the waste gases.

Other objects and advantages of the present invention will becomeapparent from the following description taken in conjunction with thedrawing in which:

Fig. 1 is a diagrammatic view of my apparatus indicating an electricalhookup used and the manner of connection with a conventional gas firedfurnace; and

Fig. 2 is a perspective view shown partly in section of an arrangementof elements within my analyzing cell.

Generally speaking, my invention contemplates conducting a clean sampleof the stack gases at a predetermined rate and at a. predeterminedtemperature, and mixed with a predetermined quantity of atmospheric air,through a cell com- 10 posed of a heated filament and a target 01 plateadapted to receive electrons from the heated filament at a rate whichvaries directly with the amount of combustibles present in the gasespassing therethrough. The heated filament causes 15 combustion of thesaid combustible gases with the oxygen in the admixed air, causing it toionize the gaseous particles and facilitate the transmission ofelectrons from the filament to the target or plate.

As the electrons impinge upon the target or plate, they cause thevoltage or current to vary in accordance with the rate of impingement.This voltage or current variation may then be amplifieciin any suitablemanner, its value regg istered, and, if desired, recorded continuously.

Referring now more particularly to Fig. 1, reference character 4designates a gas fired furnace such as a regenerative glass furnacehaving checkerwork regenerators 5 and 6 which alter- 30 natelycommunicate with a stack 1 through the regenerator canals 8 and 9, areversing valve l0, and a stack canal H. At predetermined intervals thereversing valve II] is reversed, first, to admit air through the airintake l2 through, for 335 example, regenerator canal 8, to theregenerator 5, during which interval the exhaust gases pass throughregenerator 6, the regenerator canal 9, the stack canal II, and thestack 1; and then, after a suitable interval, when the reversing valve40 Ill is reversed, the air is admitted into regenerator 6, and theexhaust gases pass through regenerator 5 out through the stack 1.

It is the purpose of the present invention to analyze the exhaust gasespassing through the canals 8, 9, and/or l0, and accordingly suitableconduits l5, l6 and I! may be provided communicating with these canalsrespectively, these conduits leading to a selector valve [8, and then 50through a suitable filter and drier l9. This drier may be supplied withcalcium chloride or other suitable substance adapted to remove the waterfrom the gas sample. The removal of water and foreign particles protectsthe internal parts of 55 the apparatus from corrosion or clogging aswell as preventing faulty readings.

The sample may then be mixed with a suitable quantity of oxygen or airwhich may be drawn through the inlet means 20 and mixed in the mixingchamber 2|. The exact proportion in which the air and gas sample may beintermixed may be regulated by means of the valves 23 and 24,respectively. Orifices 25 and 26 and accompanying manometers 21 and 28,respectively, may be provided to indicate the relative rates ofadmixture of the gases and the proportions thereof.

From the mixing chamber 2|, the sample is drawn by means of a suitablevacuum pump or exhausting means such as an aspirator 30 through theconduit 3| and through the ignition cell 32.

Suitable proportions of air to waste gas for relatively low percentageof combustibles, as, for example, less than about three per centcombustibles, may be about 1 to 1. The rate of passing the gases throughthe cell 32 may be any desired rate, although I have found that a totalof 500 cc. per minute, or 250 cc. of air and 250 cc. of waste gas perminute to be satisfactory. The air needs only be added to the sample inthe event that there is no excess air in the waste gas issuing from thefurnace. If there is suflicient air or free oxygen present in the wastegas sample, the appartus will continue to record the combustiblespresent in the gas.

The cell 32 is provided with a filament 35, which is preferably composedof a noble metal such as platinum or alloys thereof, owing to itscatalytic properties and to the fact that it has a much higher meltingtemperature compared to other elements which oxidize at elevatedtemperatures in the presence of oxygen. A variable transformer 38consisting of a primary 31 communicating with a power line 38, and asecondary 39, communicating with the filament 35, supplies sufiicientcurrent for the filament 35.

The cell 32 is also provided with a target, plate or element 40 to whichelectrons travel from the filament 35, and cause a fluctuation of thevoltage or current of plate 40.

The plate 40 is directly connected to an ainplifying means comprisinga'tube 45 consisting of a filement 46, a grid 41 to which the plate 40is electrically connected, and a plate 48'. The filament 45 may beenergized by an individual secondary 49 of the transformer 36 operatingfrom the same primary 31 as the secondary 39. A resistor 5| may beprovided between the secondary 49 and the filament 46 for adjustmentpurposes. The plate 48 is also electrically connected to the secondary49 of the transformer through a voltage indicator 53 and a B battery 54which may supply any suitable voltage.

I have found satisfactory results may be obtained with a voltage ofabout 45 volts in the B battery 54 when the voltage of the power line 38is about-110 volts. A recorder 56 may also be provided in connectionwith the indicator 53 in order to continuously record the voltage fiuctuations of the plate 48 as registered by the indicator 53. The voltagefluctuations recorded may be from 0 to about 50 millivolts.

From the particular characteristics of the tube 45, the plate voltageshould preferably be adjusted by means of the resistor 5| so that, withminimum changes in grid voltage 41, a straight line grid voltage toplate current 48 is obtained, whereby the percentage of combustibles isdirectly, although not necessarily uniformly, proportional to the platecurrent. In other words, the plate voltage should be adjusted so that afairly uniform scale may be obtained. Ordinarily, the range of theindicator 53 and recorder 56 in per cent combustibles as expressed inmillivolts, indicated and recorded, will determine the voltage to beused at the plate 48.

In order to adjust theindicator 53 to zero in per cent of combustibles,I preferably provide a variable condenser 60 having any suitable rangeof capacitance, generally in the range of about .001 microfarad, as abypass around the cell 32. Thus, the condenser 50 may be electricallyconnected between the plate 40 and the filament 35.

For a detailed view of cell 32, showing a. preferable embodimentthereof, reference may be had to Fig. 2 in which the filament is in theform of a small coil composed of a platinum wire, and the plate ortarget is in the form of a small screen disposed cylindrically aroundthe filament 35. The element or plate 40 may be composed of any suitablemetal such as brass or nickel or a suitable alloy. The operatingtemperature of the plate 40 is relatively cold compared to thetemperature of the filament 35. Ordinarily, the plate 40 may berelatively small as, for example, one inch square or so, in order toproduce satisfactory results, although the size may be varied as desiredwithin wide limits. The cell 32 may be enclosed in any suitable vesselsuch as a glass container or the like.

In operating the device, the sample of gas to be analyzed is cleaned andintermixed with a constant proportion of air, and is fed through thecell 32 at a constant rate by means of the vacuum pump 30. As the gaspasses through the cell 32, it is ignited by the filament 35 which isheated to the ignition temperature of at least about 1250 to 1400 F.which is sufiiciently high to ignite the various combustibleconstituents which may be present in the gas. Among these, the mostimportant is generally carbon monoxide, although hydrogen, ethane,methane, and other constituents may be present. The filaments should besufficiently hot in order to ignite any of the gases which may passthrough the cell 32. As the combustibles are ignited by the filament 35,the conductivity of the gaseous medium between the filament 35 and theelement 40 increases in direct proportion to the percentage ofcombustibles present. In other words, the gaseous medium between thefilament 35 and the element 40 is ionized in direct proportion to thepercentage of combustibles present in the gas which are caused to igniteby the heat of the filament 35. The change in electron fiow passingthrough the cell 32 from the filament 35 to the element 40 changes thepotential at the grid 41 in the tube 45, this change being amplified onthe plate 48 and from there indicated by the indicator 53, and ifdesired, recorded by the recorder 56. The indicator may be a sensitivevolt meter recording the voltages from about 0 to about 50 or 100millivolts, and these millivolts may be calibrated against percentage ofcombustibles present.

In adjusting the device at the start of operations, the indicator 53 maybe made to assume a positive reading, this potential reading resultingfrom the constants, (l) the capacity of the vari able condenser 60, (2)the filament current in tube adjusted by resistor 5|, (3) the distancebetween the filament 35 and the plate 40 in cell 32, and (4) the rate ofelectron or current flow through the cell when air and no waste gasesare passing therethrough. The function of the condenser 80 is to adjustthe indicator 53 to zero in percent of combustibles when air and nowaste gases are passing through the cell. The number of millivolts thenindicated by the indicator 53 becomes zerocof combustibles on the scale.

Various other applications may be made with my novel apparatus as, forexample, it may be used as a flame indicator or to operate a relay tosignal when flames are present in stacks or other parts of gas firedfurnaces. In this event, however, of course, no orifice or pumpingsystem is required, and the elements of cell 32 would merely be locatedin the region requiring observation. However, in this event, theelements in cell 32 should preferably be properly insulated andshielded. when flames-are present, the electrical conductivity betweenthe filament 35' and the element 40 increases, and thus permits thepresence of flame to be made manifest.

Various modifications and variations maybe resorted to without departingfrom the spirit and scope of the present invention, as, for example,rectified alternating current may be used-in place of that supplied bybattery 54.

I claim:

1. The method of measuring the degree of combustibles in a gas, whichcomprises igniting the combustibles in the gasand simultaneouslyregistering the electrical conductivity change in the gas as the saidcombustibles are ignited.

2. The method of analyzing a waste gas sampie to determine the degree ofcombustibles remaining therein, which comprises admixing suflicientoxygen with said gas to permit complete oxidation of the combustiblestherein, raising the gas mixture to ignition temperature of saidcombustibles to cause combustion of said combustibles, passing anelectrical current through said combustible matter in a waste gas samplewhich j comprisesa cell," means for passing a sample of gas as thecombustibles are being ignited, and indicating the amperage changesof-said current.

3. The method of analyzing stack gas containing combustible gases, whichcomprise s adding to said stack gas sufllcient oxygen to permit completecombustion of the combustible gases, passing said mixture of gas betweena heated filament and a plate, the temperature of said filament beingsufiiciently high to permit com plete combustion of said combustiblematerial in said gases, passing electrons through said gases from saidfilament to said plate, and measuring the changes in the electron flowcaused by said combustion.

4. The method of analyzing stack gas contain-, ing combustible gases,which comprises adding to said stack gas suiiicient women to permitcomplete combustion of the combustible gases, passing said mixture ofgas between a heated filament and a plate, the temperature of saidfilament being sumciently high to permit complete combustion of saidcombustible material in said gases, passing an electrical currentthrough saidgases between said filament and said plate, amplifying saidcurrent changes. caused by said combustion, and indicating saidamplified current changes.

5. The method of determining the degree of combustible gases in a wastegas sample, which comprises igniting said combustible gases with oxygenin the presence of a catalyst, and registering the electricalconductivity of the gases as the combustible matter is burning, theelectrical conductivity varying in direct proportion to the percentageof combustible matter in said waste ases. I V l 6. Apparatus -forindicating the percentage of combustible matter in a waste gas samplefrom a gas fired furnace, which comprises a cell, means for passing asample of said waste gases through said cell at a constant rate, meansfor admixing a sufiicient quantity of air with said waste gases in saidsample prior to entering said cell to cause complete combustion thereof,a filament within said cell, means to energize said filament withalternating current to at least combustion temperatures of saidcombustible matter, an element spaced apart i'rom said filament andadapted to receive electrons emanating from said heated filament, andmeans for amplifying and registerregistering the amplified rate ofelectron flow from said tube, and a capacitance shunting said filament.and the electrical connection between said grid and said element V r 7.Apparatus for indicating. the percentage of waste gases throughsaid'cell ata constant rate and admixed with sufllcient oxygen tooxidize the combustible'matter in said cell and cause com- :pletecombustion thereof, a filament within said .the grid thereofelectrically connected to said target, alternating current energizingmeans for the filament of said detector tube, means for registering theelectrical energy emanating from the plate of said detector tube, and acapacitance shunting the filament within said cell with the electricalconnection between said grid and said DOMINIC'K m0.

